Ruthenium

MELTING POINT: 2,310°C
BOILING POINT: 3,900°C
DENSITY: 12.2 g/cm³
MOST COMMON IONS: Ru²⁺, Ru³⁺, RuO₄²⁻, RuO₄⁻

Ruthenium was discovered in 1844 in ores extracted from the Ural Mountains in Russia by Karl Klaus, who named it after Ruthenia, the Latin name for Russia. Its abundance in Earth's crust is about 0.0001 ppm. Ruthenium crystallizes in the hexagonal close-packed arrangement, is lustrous, and is silvery in color. It is used primarily to harden platinum and palladium in alloys. It is extracted from platinum metal ore concentrates and isolated as a gray powder or a sponge using chemical techniques. Ruthenium will dissolve in fused KOH to give K₂[RuO₄]. It will react with F₂ to give RuF₅, and with Cl₂, Br₂, or I₂ to yield RuX₃, where X = Cl, Br, or I. It also combines with the elements As, P, Si, and B at high temperatures to form binary compounds of various stoichiometries, and with air upon heating to yield RuO₂. RuO₄ (mp 25.5°C, or 77.9°F), a powerful oxidizing agent, is obtained by reaction of ruthenium in acidic solution with oxidizing agents such as MnO₄₋ and has found use as a catalyst in the oxidation of various substrates. In the +2 and +3 oxidation states, ruthenium forms numerous coordination complexes with ligands containing carbon, nitrogen, phosphorus, oxygen, and sulfur donors. It also forms oxo- and ligand-bridged binuclear and trinuclear metal complexes, such as [(NH₃)₅Ru–N–N–Ru(NH₃)₅]⁴⁺ and [(NH₃)₅Ru–O–Ru(NH₃)₄–O–Ru(NH₃)₅]⁶⁺ , and dioxo-compounds such as cis- or trans- [Ru(bpy)₂(O)₂], where bpy is 2,2′-bipyridine. In the lower oxidation states, ruthenium together with carbonyl, phosphine, and/or hydrido ligands form alkene, diene, alkyne, and allyl complexes.

SEE ALSO PALLADIUM; PLATINUM.

D. Paul Rillema

Bibliography

Cotton, F. Albert, and Wilkinson, Geoffrey (1988). Advanced Inorganic Chemistry, 5th edition. New York: Wiley.

Greenwood, N. N., and Earnshaw, A. (1984). Chemistry of the Elements. New York: Pergamon Press.